Abstract

BACKGROUND
Recently, many studies have focused on human epidermal growth factor receptor 2 (HER2) status in gastric cancer due to HER2-targeted therapy using trastuzumab. We investigated HER2 overexpression and amplification and their concordance rate in Korean gastric adenocarcinomas.
METHODS
Tissue microarrays were constructed with 232 gastric adenocarcinoma samples. We performed immunohistochemistry (IHC), silver-enhanced in situ hybridization (SISH) and fluorescence in situ hybridization (FISH) for HER2.
RESULTS
IHC was negative in 94.8% (218/232), equivocal in 1.7% (4/232) and positive in 3.5% (8/232) of cases. HER2 protein expression was heterogeneous in 75% (9/12) of IHC 2+/3+ cancers. Gene amplification was observed in 6.5% (15/230) by SISH and the same 15 cases were also FISH-positive. We observed HER2 amplification in 1.4%, 27.3%, 25%, and 100% of IHC 0, 1+, 2+, and 3+ gastric adenocarcinomas, respectively. The concordance rate between IHC and SISH results was 95.7%.
CONCLUSIONS
HER2 overexpression and amplification were less frequent in gastric adenocarcinomas than breast carcinomas. Compared to breast carcinoma, (1) there may be IHC-negative but gene amplification-positive cases for HER2 and (2) frequent intratumoral heterogeneity of IHC for HER2 in gastric adenocarcinomas.

• Keywords: Stomach neoplasms;HER2, human;In situ hybridization, fluorescence;Silver;In situ hybridization;